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Lion Air 737-800 MAX Crashes Into Java Sea Shortly After Departure-No Survivors

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joeyb747:
They are looking at possibly faulty AOA sensors on ALL 737-800/-900 MAX Series aircraft.

An Emergency AD has been issued:

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/83ec7f95f3e5bfbd8625833e0070a070/$FILE/2018-23-51_Emergency.pdf

Below is from the updated AvHerald article:

"On Nov 7th 2018 Boeing issued an Operations Manual Bulletin (OMB) to all Boeing 737 MAX Operators stating that the investigation into the crash of PK-LQP found one of the Angle of Attack Sensors had provided incorrect readings, which could cause the aircraft's trim system to uncommandedly trim nose down in order to avoid a stall during manual flight. The OMB directs "operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor." The OMB reiterates the Stabilizer Runaway non-normal checklist.

The flight Crew Operations Manual Bulletin TBC-19 reads:

The Indonesian National Transportation Safety Committee has indicated that Lion Air flight 610 experienced erroneous AOA data. Boeing would like to call attention to an AOA failure condition that can occur during manual flight only.

This bulletin directs flight crews to existing procedures to address this condition. In the event of erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds. The nose down stabilizer trim movement can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after the electric stabilizer trim switches are released. Repetitive cycles of uncommanded nose down stabilizer continue to occur unless the stabilizer trim system is deactivated through use of both STAB TRIM CUTOUT switches in accordance with the existing procedures in the Runaway Stabilizer NNC. It is possible for the stabilizer to reach the nose down limit unless the system inputs are counteracted completely by pilot trim inputs and both STAB TRIM CUTOUT switches are moved to CUTOUT.

Additionally, pilots are reminded that an erroneous AOA can cause some or all of the following indications and effects:

- Continuous or intermittent stick shaker on the affected side only.
- Minimum speed bar (red and black) on the affected side only.
- Increasing nose down control forces.
- Inability to engage autopilot.
- Automatic disengagement of autopilot.
- IAS DISAGREE alert.
- ALT DISAGREE alert.
- AOA DISAGREE alert (if the AOA indicator option is installed)
- FEEL DIFF PRESS light.

In the event an uncommanded nose down stabilizer trim is experienced on the 737 - 8 / - 9, in conjunction with one or more of the above indications or effects, do the Runaway Stabilizer NNC ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight."

From:

http://avherald.com/h?article=4bf90724&opt=0

wiedehopf:

--- Quote ---They are looking at possibly faulty AOA sensors on ALL 737-800/-900 MAX Series aircraft.

--- End quote ---

Not quite how i understand the reports. The problem is that the stall protection commands A LOT of nose down trim in case of a SINGLE AoA sensor failure.

A single sensor failure should not lead to such a dangerous flight input ESPECIALLY in manual flight.

joeyb747:

--- Quote from: wiedehopf on November 08, 2018, 10:58:19 AM ---
--- Quote ---They are looking at possibly faulty AOA sensors on ALL 737-800/-900 MAX Series aircraft.

--- End quote ---

Not quite how i understand the reports. The problem is that the stall protection commands A LOT of nose down trim in case of a SINGLE AoA sensor failure.

A single sensor failure should not lead to such a dangerous flight input ESPECIALLY in manual flight.

--- End quote ---

While I agree with you that a single sensor failure shouldn't lead to this, apparently it can...

From the AvHerald article:

"On Nov 7th 2018 Boeing issued an Operations Manual Bulletin (OMB) to all Boeing 737 MAX Operators stating that the investigation into the crash of PK-LQP found one of the Angle of Attack Sensors had provided incorrect readings, which could cause the aircraft's trim system to uncommandedly trim nose down in order to avoid a stall during manual flight. The OMB directs "operators to existing flight crew procedures to address circumstances where there is erroneous input from an AOA sensor." The OMB reiterates the Stabilizer Runaway non-normal checklist."

If it's not the sensor sending faulty data, it's how the system is interpreting it... Here's the EAD, the above link isn't working...

https://theaircurrent.com/wp-content/uploads/2018/11/B737-MAX-AD-1107.pdf

ORD Don:

   
     https://www.cnn.com/2019/01/14/asia/lion-air-cockpit-voice-recorder-intl/index.html   


 " Lion Air's operational director has accused Boeing of withholding information from pilots in the manuals about the feature that automatically lowers the airplane's nose to
   prevent or exit a stall.
   Boeing chief executive Dennis Muilenburg told Fox Business Network in November that information was available as part of the training manual."

   It seems to me like Boeing should make it VERY CLEAR when a feature like this has been added/modified ?

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